Heat reacting butyl rubber, halogenated butyl rubber and zinc oxide, and composition obtained thereby



; L. T. EBY ETAL' HEAT REACTING BUTYL. RUBBER HALOGENATED BUTYL RUBBER .AND. ZINC OXIDE. AND COMPOSITION OBTAINED THEIREBY Filed Aprll 4, 1957 RUN INVENTORS Lawrence T Eby Robert M. Thomas BY vii/ ATTORNEY United States Patent HEAT REACTING BUTYL RUBBER, HALOGEN- ATED BUTYL RUBBER AND ZINC OXIDE, AND COMPOSITION OBTAINED THEREBY Lawrence T. Eby, Linden, and Robert M. Thomas, Westfield, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Apr. 4, 1957, Ser. No. 650,647 13 Claims. (Cl. 260-415) This invention relates to improved methods of processing or finishing rubbery homopolymers or copolymers such as high molecular weight rubbery polymerization products of isoolefins or mixtures of 85 to 99.5% of isoolefins and 15 to 0.5% of multiolefins, including such operations as milling, calendering, or especially extruding. High molecular weight polyisoolefins such as polymers of C to C isoolefins including 2-methyl-l-butene, 3- methyl-l-butene and especially isobutylene or the like, or copolymers of the type of butyl rubber containing about 85 to 99.5 weight percent of such C to isoolefins and about to 0.5 weight percent of C to C multiolefins (preferably conjugated diolefins) such as butadiene, dimethyl butadiene, piperylene, cyclopentadione, vinyl fulvenes, and especially isoprene, may be produced at temperatures of between about 30 to -160 C. using a Friedel-Crafts catalyst and a C to C alkyl halide polymerization diluent such as methyl chloride. Copolymers so produced generally have Wijs iodine numbers between about 0.5 and 50.5. When such copolymers or homopolymers have viscosity average molecular weights of between about 300,000 and 15 million or especially between about 500,000 and 10 million, their rate of extrusion, milling or calendering is relatively slow. The extrudates formed also generally do not have a smooth appearance and tend to become swelled during extrusion. It has been proposed to correct this situation by the use of large amountsvof certain types of fillers such as about 100 or 150 parts by weight of various clays or carbon blacks per 100 parts by weight of polymer or copolymer. However, this procedure has not been entirely satisfactory for either such homopolymers or copolymers as the foregoing because even then entirely smooth extrusion cannot be made with the higher molecular Weight polymers and the physical properties of the extruded rubber with high loading are not a match for those with less filler present.

' In accordance with the present invention, the abovementioned disadvantages are overcome and such homopolymers and copolymers as those hereinb'efore mentioned are rendered easily extruded, milled, or calendered by heating the same prior to finishing for several seconds to about 30 minutes or more, preferably for about 0.5 to minutes at about 200 to 400 F. preferably at about 250 to 350 F., with .a minor proportion, preferably about 10 to 40 weight percent of a composition comprising a halogenated rubbery isoolefin-multiolefin copolymer having a viscosity average molecular weight of between about 50,000 and 1,000,000 and about 2 to 30, preferably about 3 to 20 parts by weight, per 100 parts by weight of total polymers, of zinc oxide. The heat treatment may also optionally be performed in'the presence of accelerators such as thiocarbamic acid derivatives including alkyl thiuram sulfides, metallodialkyl thiocarbamates; mercaptobenzothiazole or derivatives of mercaptobenzothiazole such as benzothiazyl disulfide, and/or phenol-dialcohol "ice resins of the polymethylol phenol type in addition to the zinc and oxygen-containing compound. Such auxiliary materials may be used in amounts of about 0.05 or 2.0 parts by weight per 100 parts by weight of total polymers up to an amount approximately equivalent in weight to the zinc and oxygen-containing compound, the only prerequisite being that the amounts of such materials are insuflicient to cause the unhalogenated copolymer to undergo substantial vulcanization during heating.

In the case of rubbery isoolefin-multiolefin copolymers, the heat treated mixture formed may then be extruded, calendered, or milled with facility and cooled to below about 250 F. and preferably below about 150 F. with the addition of such conventional compounding ingredients as sulfur, carbon blacks or mineral fillers, sulfurcontaining accelerators and/ or quinone dioxime or derivatives of quinone dioxime, and/ or primary or polyfunctional amines, and/ or additional zinc oxide if needed, and/or polymethylol phenol resins, plasticizers, stearic acid, etc. and subsequently vulcanized as more fully described hereinafter. It has also been found that such compounded stocks formed may be extruded or calendered prior to vulcanization more smoothly and rapidly than when no halogenated rubbery isoolefin-multiolefin copolymer has been added or when the halogenated rubber is replaced by an unhalogenated rubbery isoolefinrnultiolefin copolymer of comparable molecular weight.

It has also been found that high molecular weight polyisobutylene and other polymers of C to C isoolefins may be processed, as by extrusion, calendering, milling or the like, with facility by the process of the present invention. However, since the addition of compounding ingredients such as'fillers, resins, and plasticizers is optional in the case of polyisoolefins, the extrusion or calendering may be performed on the stock directly from the heat treatment. Both such copolymers and polyisoolefins as above mentioned, because of the heat treatment with halogenated isoolefin-multiolefin copolymers and zinc and oxygen-containing compounds, in accordance with the present invention, exhibit a combination of reduced nerve and reduced cold flow. Also, vulcanizates of isoolefin-multiolefin copolymers which have been processed in accordance with the present invention, when cured for about 10 to minutes at temperatures between about 275 and 450 F. exhibit improved physical properties such as a decreased permanent set. i

The halogenated isoolefin-multiolefin copolymer to be heat interacted in the presence of zinc and oxygen containing compounds with the polymeric materials in accordance with the present invention may be prepared by the mild chlorination or bromination of the unhalogenated hydrocarbon copolymer commonly known as Butyl rubber. The preparation of Butyl rubber is described in US. Patent 2,356,128 as well as in the book Synthetic Rubber by G. S. Whitby. The halogenation is preferably carried out so as to make the resulting halogenated Butyl rubber contain at least 0.5 weight percent and preferably at least about 1.0 weight percent combined chlorine or bromine but not more than about X weight percent chlorine or 3.0 X weight percent bromine wherein:

X L M.+L M.+M. and:

L=mole percent of the multiolefin in the polymer M =molecular weight of the isoolefin M =molecular weight of the multiolefin M =atomic weight of chlorine or bromine sulfuryl bromide, sulfuryl chloride, pyridinium chloride perchloride, N-brorno succinimide, N,N'-dichloro dimethyl hydantoin, alpha-chloroaceto acetanilide, iodine monochloride, tribromo phenol bromide, N-chloro-acetamide, beta-bromomethyl phthalimide, etc. The halogenation is advantageously conducted at temperatures of between above C. to about 100 C., preferably at about 20 to 80 C. for about one minute to several hours. However, the temperatures and times are regulated to halogenate the rubbery copolymer to the extent above-mentioned.

The halogenation may be accomplished in various ways. One process comprises preparing a solution of the copolymer as above in a suitable inert liquid organic solvent and adding thereto chlorine or bromine or other halogenating agent optionally in solution, such as dissolved in an alkyl chloride, carbon tetrachloride, etc. In this instance the low molecular weight rubbery copolymer is halogenated separately and subsequently added to the high molecular weight unhalogenated rubbery copolymer. The solvent is then stripped out and the zinc and oxygen-containing compound added with a subsequent heat treatment prior to vulcanization of the unhalogenated high molecular weight copolymer in accordance with the invention.

Another method resides in blending with the low molecular weight copolymer a solid halogenating agent such as N-bromo or chloro-succinimide, N,N-dichloro or dibromo dimethylhydantoin, or other solid halogenating agent. In such a case, the resulting mixture is preferably mill-mixed and heated to a temperature suflicient to halogenate the solid copolymer. It is also within the purview of the present invention to blend the low molecular weight copolymer with a solid borminating or chlorinating agent such as those above-mentioned and to heat the blend formed to a temperature suflicient to brominate or chlorinate the solid low molecular weight copolymer in situ. In all of the foregoing instances, the use of elevated or depressed pressures are optional since atmospheric pressure is satisfactory. However, the pressure may vary depending upon the foregoing temperatures, reaction times and particularly halogenating agents from about 0.5 to 500 p.s.i.a.

In order to more fully illustrate the present invention, the following experimental data are given:

Example I Samples of a high molecular weight butyl rubber copolymer having a viscosity average molecular weight of 920,000 and a mole percent unsaturation of 1.2 (hereinafter referred to as H.M. butyl rubber) were compounded with 5.0 parts by weight of zinc oxide (per 100 parts by weight of total rubber) with and Without an added lower molecular weight chlorinated butyl rubber (hereinafter referred to as chlorinated butyl rubber A) or an added unmodified low molecular weight butyl rubber (hereinafter referred to as L.M. butyl rubber). Chlorinated butyl rubber A" had a Mooney viscosity at 212 F. for 8 minutes of 50, a mole percent unsaturation of 1.6, and a chlorine content of 1.30 Weight percent based on the rubber. The unmodified L.M. butyl rubber had a Mooney viscosity at 212 F. for 8 minutes of 50 and a mole percent unsaturation of 1.6. All samples were hot milled for 10 minutes at 310 F. and then compounded with 50 parts by weight, per 100 parts by weight of total rubber, of MPC carbon black and extruded through a Garvey die at 220 F. and 80 r.p.m.

The proportions of ingredients and appearance of the extrudates were as follows:

Parts by weight Run 1 2 3 4 4-a l H.M.butyl 100 80 8O 80 rubber.

Chlorinated 10 20 butylrubberA".

L.M. butyl 20 20.

rubber.

Zincoxide. i 5 5 5 5.

MP0 carbon 50 50; 50 50 50.

black.

Extrusion very smooth. very very very appearance. rough. smooth. rough rough.

1 Run 4-a had no heat treatment.

Referring now to the accompanying drawing, the four photographs which are designated runs 1, 2, 3, and 4 show sections of the firstfour above extrusions. It can be seen. that the extrudates from run 2 and especially from run 3, in accordance with the present invention, are considerably smoother in appearance than the extrudates having no added chlorinated butyl rubber (run 1) or having added unmodified low molecular weight butyl rubber (runs 4 and 4-a).

One hundred parts by weight each of the above rubber stocks of runs 1, 2, 3, and 4 were each compounded on a rubber mill at room temperature with 1.5 parts by weight of sulfur and 1.0 part by weight of tellurium diethyl dithiocarbamate and the resulting blends vulcanized by heating for 40 minutes at 307 F. The following physical inspections of the cured vulcanizates were noted of which the appearance is a visual rating of the cross section of cylindrical slugs cut in half after the standard Goodrich Flexometer test at 0.25 inch stroke, a frequency of 32 cycles per second, operating for 30 minutes at C. (212 F.) with a 15 pound weight (i.e. equivalent to 89 p.s.i.). The appearance rating was in accordance with the following table:

Appearance: Rating No porosity 1 Slight porosity 2 Very porous 3 Broken in center (not porous) 4 Large hole in center and porous 5 The data was as follows:

Rubber Stock No 1 2 3 4 Modulus at 300% Elong. (p.s.i.) 920 930 1200 875 Tensile strength (p.s.i.).- 3090 3290 3080 2840 Elongation (percent)-.. 740 750 630 670 Shore "A" hardness... 57 54 58 58 Permanent set (percent) 22. 7 17. 9 18.2 20.5

Max. temp. rise (1).--- 29 2O 30 Appearance 5 2 2 5 The above data show that the vulcanized rubber stocks 2 and 3, which had been thermally treated with chlorinated butyl rubber and zinc oxide, in accordance with the present invention, prior to vulcanization, cured into vulcanizates of improved (i.e. lower) permanent set and of much better appearance.

Example II of extrudates from a Garvey die extruded as in Example I were as follows:

for minutes at 310 F. and compounding with 50 parts by weight of MPC carbon black, the following Garvey extrusion data were obtained:

Parts by weight R bb st k Rubber Stock o 5 6 7 Control 12 1a 14 C n t: r

ri /fi lmtyl rubber 9o 90 90. nllgf mn m OhlorinatedbutylrubberA 10 10 Chlorinated 9n so 40 20.

Bromiuated butyl rubber B" 10. 10 butyl rub- Zinc oxide 5 5 5. her A. a

MPC carbon black 50 50 50. Hydrocarbon 15.

Hydrocarbon plasticizer oil 2 15 Plasticizer Appearance Very h Smooth- Smooth. EciiL m m 69 9 5 rolls 7 s.

, or asms, Y o 15 minute). 1 Rubber stocks 6 and 7 were hot milled for 10 minutes at 310 F. before Swell dex 1,86 1,29 1.18 1.33 1.31. the addition of the carbon black and plasticizer 011 except stock No. 5 (cc /i11ch). in which all ingredients were added before hot milling. Appearan cc of very smooth very very smooth.

2 The hydrocarbon plasticizer oil employed was derived from a naphtr date, r u h, smooth, smooth. thenie base crude and had the following properties:

. 1 The hydrocarbon plasticizer oil employed was derived from a naph- PTODQTW p y glggg thenic base crude and had the same properties as in Example II.

a The above data show that the extrusion of polyisobutyli i s l i go iii i ii$1 0560;100256651: 122 280 520 6116 is improved by heath-eating 10 minutes at Viscosity (s'sU. at100 F 510 50-2, 000 F. in the presence of zinc oxide and chlorinated butyl i2 6% rubber. There is noted an increase in smoothness and extrusion rate with increased chlorinated butyl rubber The above data show that the extrud-ates of rubber addimn of the hydrogen-hon pllgsticizer oil increase t e rate 0 extrusion wit out sacr' ce in surstock numbers 6 and 7 of the present mvennon are face smoothness It will also be noted that the swell ig gg z g g i gf i ggz gg'giyig gi its: index of all rubber stocks processed in accordance with ing procedure for rubber stock 5, in which the heat treatg fi fi fs i gg igg ghi' 55322 12 to 15) exhlblted a menbt 1 lager (rather 3 g ofhthe Resort may be had to various modifications and variacar on ac was unsatis actory. e ata so s ow tions of the disclosed embodiments of the resent inventhat elther chloqnated butyl 'mbber or ated butyl tion without departing from the spirit of th invention or rubber are effective for heat treatment with high molccuthe Sco e of the a ended claims lar weight butyl rubber in thepi'esence of a zinc and whagis c1aime oxygen'c-ontanimg compound accordan-C? Wlth the l. Ina method for processing a polymer selected from present invention, to improve its processability (e.g. to the group consisting of homopolymem of 4 to C7 is? Improve extruslon) 40 olefins, isoolefin-multiolefin butyl rubber copolymers, and

Example mixtures thereof, said polymers having viscosity average The same general procedure as in Example I was again molecular weights of between about 300,000 and 15,000, repeated on four samples of high molecular weight butyl the improvement which comprisfis heating Said rubber using 5 parts by weight of zinc oxide prior to pg ij F 83 p g zg g g l h p l level heat treating and 50 parts by wei ht of MPC carbon etweell a out 2 an Wlt 11111101 P black after heat treating for 10 minu ies at 310 F. Addi- 1 of an admixture of a halggenated q pfi tional compounding data, swell index and appearance of Olefin y rubber p t e halogen 111 Sald h extrudates were as foll w ggnateil lcopollyrner healing an atomic number of at least a out an zinc oxi e. Partsby weight 2. A method according to claim 1 in which the polymer is compounded after heating with a minor propor- Rubber Stock No a 9 i0 11 tion of a carbon black- I 3. A method according to claim 1 in which the unoomponemz halogenated polymer is a butyl rubber copolymer of y 90 80 70 about 85 to 99.5 Weight percent of isobutylene and a g gfg 10 20 30 minor proportion of a C to C multiolefin, said unhalobu g u genated polymer having a viscosity average molecular 3 index 1,40 L24 L17 no weight of about 500,000 to 10,000,000.

-fi th th 4. A method according to claim 1 in which the un- Appearance smoo s i nooth s glooui. Smoo halogenated polymer is polyisobutylene havingaviscosity average molecular weight of between about 500,000 and The above data show that extrudates of good appear- 10,000,000-

:ance and low swell index are produced in accordance with h A z g i z 2 523 g zg qgl the present invention when using 10 to 40 weight percent zif g i gg sfilfur fi gg g for abut of chlorinated butyl rubber based on total rubber present. 10 to. 10 P z at a temperature level of between about Example IV 275" and 450 F.

The same general procedure as i Example I was 6. An improved isoolefin-multiolefin butyl rubber coagain repeated substituting a polyisobutylene of 9,300,000 Polymfipcontalmng vulcapllate hilvlng a Permanent Set viscosity average molecular weight for the high molecu- 3 2 2) 12 t h 2 l l g havmg been p lar weight butyl rubber. The polyisobutylene was com 1106 Y me 0 0 alm pounded with 5 parts by weight of Zinc oxide and the 7. In a method for processing a polymer selected from various amounts of chlorinated butyl rubber A indithe group consisting of homopolymers of C to C iso- -cated hereinafter and compared to a control containing olefins, isoolefin-mul tiolefin butyl rubber copolymers and n0 chlorinated butyl rubber A. After heat treating mixtures thereof, said polymers having viscosity average molecular weights of between about 300,000 and 15,000,000, the improvement which comprises heating said polymer, prior-to such processing, at a temperature level of between about 200 and- 400" F. for between about 0.5 to 30 minutes with about 2 to 40 weight percent based on said polymer of an admixture of the reaction product of an unmodified isoolefin-multiolefin butyl rubber copolymer having a viscosity average molecular weight of about 50,000 and 1,000,000 with a halogenating agent having an atomic number of at least about 17, and zinc oxide.

8. A method according to claim 7 in which the zinc oxide is present in an amount of between about 10 and 30 weight percent based on the polymer having a viscosity average molecular weight of between about 300,000 and 15,000,000.

9. A method according to claim 7 followed by compounding the resulting heated polymeric mixture with a minor proportion of carbon black.

10. A method according to claim 7 in which the polymer having a viscosity average molecular weight of about 300,000 to 15,000,000 is an isoolefin-multiolefin butyl rubber copolymer, said copolymer, after heating, having been compounded with a minor proportion of sulfur and a viscosity average mol. wt. of about 300,000 to 15,000,000, a minor proportion of a halogenated isoolefin-multiolefin butyl rubber copolymer containing at least 85% of isoolefin, in which the halogen has an atomic number of at least 17, and zinc oxide.

12. Composition according to claim 11 in which the unhalogenated polymer is a polyisobutylene having a viscosity average mol. wt. of at least 500,000.

13. Composition according to claim 11 in which the unhalogenated polymer is an isobutylene-isoprene butyl rubber copolymer containing at least 85% of isobutylene, and having a viscosity average mol. wt. of at least 500,000.

No references cited. 

1. IN A METHOD FOR PROCESSING A POLYMER SELECTED FROM THE GROUP CONSISTING OF HOMOPOLYMERS OF C4 TO C7 ISOOLEFINS, ISOOLEFIN-MULTIOLEFIN BUTYL RUBBER COPOLYMERS, AND MIXTURES THEROF, SAID POLYMERS HAVING VISCOSITY AVERAGE MOLECULAR WEIGHT OF BETWEEN ABOUT 300, AND 15,000,000, THE IMPROVEMENT WHICH COMPRISES HEATING SAID POLYMER, PRIOR TO SUCH PROCESSING, AT A TEMPERATURE LEVEL OF BETWEEN ABOUT 200* AND 400*F. WITH A MINOR PROPORTION OF AN ADMIXTURE OF A HALOGENATED ISOOLEFIN-MULTIOLRFIN BUTYL RUBBER COPOLYMER, THE HALOGEN IN SAID HALOGENATED COPOLYMER HAVING AN ATOMIC NUMBER OF AT LEAST ABOUT 17, AND ZINC OXIDE. 